A new method has been added to the `CoursesController` which allows admins to fill default live video URLs for online lectures that don't have one. This feature is accessible via a button on the courses admin page. The routing for this new action has also been set up.
- Made TrackedTimeEntries polymorphic to belong to both Lecture and WorkItems models
- Added associated migrations for existing data
- Added to administrate UI
Modified code to remove 'status' field from lecture's table and added 'event_uuid' field. Also refined the 'start_time' field in recordings' table to handle datetime instead of strings. Further, made minor changes in scraping jobs and seeding logic. Implemented these changes to allow lectures to be associated with calendar events and streamlined various fields.
